Expandable bag liner



Feb. 21, 1967 J. F. LEHMAN 3,305,160

EXPANDABLE BAG LINER Filed April 16, 1965 W I:W W W W [6W ATTORNEYS 3,305,160 EXPANDABLE BAG LINER John F. Lehman, Glenside, Pa., assignor to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Apr. 16, 1965, Ser. No. 448,597 14 Claims. (Cl. 229--55) This invention relates to a novel improvement in socalled multi-ply bags, and in particular, is directed to a novel liner for multi-ply bags having means for permitting the liner to expand under the influence of pressure exerted by a product packaged in the liner to prevent the liner material from rupturing, thereby preventing the packaged product from escaping the liner or the entrance of atmosphere into the liner which might adversely affect the packaged product.

The normally constructed multi-ply bag generally includes an outer wrapper and an inner liner with the outer wrapper being constructed of relatively heavy paperstock material to give the bag requisite strength while the liner is generally constructed of thinner and weaker material of a highly impermeable nature. The impermeable material of conventional liners fuutcions to prevent atmosphere from adversely affecting a product packaged in the liner, and in the case of a grease-containing product, prevents the grease from being absorbed by the wrapper. This absorption'of the grease by the wrapper is undesirable because it weakens the strength of the Wrapper, generally causes discoloration and weakens conventional adhesive seams in the body and bottom portions of the wrapper. Therefore, commercially acceptable multi-ply bags must include liners which, under all conditions, function to maintain the structural integrity of such bags and protect products packaged therein.

In such two ply bags the periphery of the exterior surface of the inner liner is generally at least equal to the periphery of the inner surface of the outer wrapper, and a spot coating of adhesive is applied between the surfaces to secure the liner to the wrapper. The liner, as well as a product packaged therein, is supported for the most part by the wrapper. It has been found, however, that under certain circumstances, such as aging or moisture loss of the liner material, the liner material shrinks sufiiciently to lose supporting contact with the outer wrapper and ruptures under the forces (weight and/ or pressure) of the packaged product.

Even under circumstances of slight liner shrinkage which might not otherwise rupture the liner, the additional strains to which the bag is subjected, such as impact forces under normal and rough handling conditions, can cause liner rupture.

Liners of conventional multi-ply include a longitudinal seam formed by adhesively bonding terminal edges of the liner. Shrinkage of the liner and the attended reduction in the liner periphery can rupture this seam.

It is, therefore, a primary object of this invention to provide a liner which is expandable in size to compensate for liner shrinkage and thereby overcomes each of the noted disadvantages in conventional liner structures.

A further object of this invention is to provide a novel multi-ply bag including an outer wrapper and an inner liner, the liner including a generally tubular body closed at one end and constructed from foldable material, a longitudinal fold formed from the material of the body, and the longitudinal fold being defined by first, second and third opposing longitudinal portions of the body in generally parallel relationship in a first position adapted for unfolding movement toward a generally coplanar relationship in a second position whereby the liner can bags also generally United States Patent 6 ice expand and compensate for forces otherwise tending to rupture the liner.

Still another object of this invention is to provide a multi-ply bag including at least an outer wrapper and an inner liner having substantially identical peripheries, the liner being constructed from foldable material and including a longitudinal seam being defined by lapped edge portions having opposed surfaces bonded together by adhesive, the material of the liner being of a predetermined strength, and the bond strength of the adhesive of the seam being appreciably weaker than the strength of the liner material whereby any tendency of the liner to shrink under the influence of internal pressure applied to the liner by a packaged product causes partial separation of the seam thereby increasing the periphery of the liner and preventing rupture of the liner or the longitudinal seam thereof.

With the above, and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawing.

In the drawing:

FIGURE 1 is a top perspective view with parts broken away for clarity of a multi-ply bag constructed in accordance with this invention, and illustrates an expandable inner liner thereof.

FIGURE 2 is an enlarged sectional view taken generally along line 2-2 of FIGURE 1, and illustrates a longitudinal fold in the area of a longitudinal seam of the liner for compensating for shrinkage of the liner.

FIGURE 3 is an enlarged fragmentary view of the multi-ply bag of this invention taken generally along line 33 of FIGURE 1, and more clearly illustrates the longitudinal fold and longitudinal seam of the liner as well as an intermediate and outer ply of the bag.

A novel container constructed in accordance with this invention is generally referred to by the reference numeral 10 and is illustrated for purposes of describing this invention in the form of a multi-ply bag formed of an outer wrapper 11, an intermediate ply or liner 12, and an inner liner or inner ply 13. The multi-ply bag 10 is of a three-ply construction, but more or less than this number of plies may be employed in the practice of this invention.

The multi-ply bag It includes a closed bottom 14 (FIGURE 2) formed by adhesively securing together a plurality of flaps and tabs (unnumbered) of each of the plies 11, 12 and 13 in a manner well known in the prior art to form any desired bottom construction, such as a square or satchel-type bottom closure.

The outer ply or wrapper 11 includes a body 15 which is generally tubular in configuration. The body 15 includes a longitudinal seam (unnumbered) formed by adhesively securing together terminal longitudinal edge portions 16, and 17 (FIGURE 2) in a customary manner. The wrapper 15 is preferably constructed from paperstock material and includes an inner surface (unnumbered) which has a periphery substantially identical in size to the periphery of the outer surface of the intermediate ply 12.

The intermediate ply 12 is also preferably constructed from paperstock material and serves to additionally reinforce the bag 10. The intermediate ply 12 also includes a longitudinal seam (unnumbered) defined by adhesively secured terminal edge portions 18 and 20 which are staggered in relation to the edge portion 16, 17 of the wrapper 11, as is best illustrated in FIGURE 2. The intermediate ply 12 is secured to the body 15 of the wrapper 11 by the selective application of adhesive (not shown) to the outer surface of the intermediate ply 12 or the inner surface of the outer ply 11.

The liner 13 includes 'a generally tubular body 21 constructed of readily foldable flexible material which is preferably grease-proof, such as glassine. The material from which the liner i3 is constructed is generally, but not necessarily weaker, than the material of the intermediate ply 12 or the outer wrapper 11.

The liner 13 is provided with means, generally referred to by the reference numeral 25, for permitting the liner 13 to expand in peripheral and volumetric dimensions from the condition of the liner 13 illustrated in the drawings to a second condition at which the liner 13 has shrunk somewhat due to the aging or the loss of moisture from the material of the liner 21. The expandable means 25 is in the form of a longitudinal fold formed from the material of the liner 13. The longitudinal fold 25 comprises first, second and third longitudinal portions 26-28 respectively, disposed in generally opposing parallel relationship in the normal unexpanded position of the liner 13 illustrated in the drawings, but these longitudinal portions are capable of folding toward a generally planar relationship in a second expanded position (not shown) of the liner 13 as will be described more fully hereafter. The longitudinal portions 26 and 27 define edge portions of the blank which terminate in respective free edges 30 and 31 (FIGURE 2).

The longitudinal portion 27 of the longitudinal fold 25 is integrally joined along a longitudinal. fold line or juncture 29 to the portion 28. The longitudinal portion 27 is similarly joined to the longitudinal portion 26 at a similar juncture (unnumbered) adjacent the free edges 30, 31 by adhesive means 32 (FIGURE 3) in the form of a line of water-base or hot-melt adhesive, depending on the particular material from which the liner 13 and intermediate ply 12 are constructed. The adhesive 32 extends the entire length of the bag 10, including the tabs and flaps (unnumbered) defining the bottom closure 14, and in conjunction with the longitudinal portions 26 and 27, forms the longitudinal seam (unnumbered) of the liner 13.

A second line of adhesive 33 is similarly applied between the opposed surfaces of the longitudinal portions 26, 27 adjacent butspaced from both the fold line 29 and the line of adhesive 32, as is best illustrated in FIG- URE 3. The line of adhesive 33 also runs the entire length of the liner 13.

The longitudinal fold 25 is completely free of the inner surface of the intermediate ply 12. Remaining portions of the liner 13 to either side of the longitudinal fold 25, as viewed in FIGURE 2 of the drawing, are provided with spots of adhesive 35 (FIGURE 3) which secure the liner 13 to the intermediate ply 12 completely about the upper periphery of the bag 10. Except for the adhesive 35 at the upper periphery of the bag 10, the remaining opposed surface portions of the liner 13 and the intermediate ply 12 are free of adhesive.

The multi-ply bag is packaged with a suitable product, as for example, dog food, and the upper portion of the bag is closed. During subsequent storage of the packaged bag, the liner 13 may shrink for the reasons heretofore noted, and in the absence of the expandable means 25, the material of the liner 13 would rupture. However, upon the shrinkage of the liner 13 of this invention the overfolded portions 27 and 28 of the longitudinal fold 25 begin to unfold toward a coplanar position, although this latter position is never fully reached. This unfolding of the longitudinal fold 25 continues until a peripheral length of material is unfolded equal to twice the distance D (FIGURE 2) between the fold line 29 and the line of adhesive 33. The particular amount of overlap indicated by the distance D is determined by various factors, such as the particular product packaged in the bag 10, the weight thereof, the coefficient of shrinkage of the liner material etc., and under normal conditions of packaging, handling and storage complete unfolding (ZXD) .of the longitudinal fold 25 will assure adequate compensa tion for liner shrinkage and will prevent the liner from rupturing.

While the complete unfolding of the portions 27, 28 of the longitudinal fold 25 between the line of adhesive 33 and the fold line 23 is normally sufiicient to com pensate for expected liner shrinkage, the line of adhesive 33 prevents the liner 13 from rupturing after the longitudinal fold 25 has unfolded the distance 2D. This function of the line of adhesive 33 is achieved by compounding the adhesive to have a bond strength which is less than the rupture strength of the liner material. That is, the adhesive line 33 is weaker than the strength of the ma terial of the liner 13 and separates under continued shrinkage of the liner. The unfolding of the longitudinal fold 25 can then continue until resisted by the line of adhesive 32. This construction is particularly effected when the liner 13 has been unfolded a peripheral distance equal to twice the distance D and subjected to an impact force during rough handling. The force of impact, is for the most part, absorbed by the adhesive as it separates thus preventing rupture of the liner and complete separation of the liner seam.

While the bag 10 has been illustrated as being provided with two lines of adhesive 32, 33, it is also within the scope of this invention to provide a single wider line of adhesive between the opposing surfaces of the longitudinal portions 2d and 27 of the longitudinal fold 25. This single wide line of adhesive would, of course, be of a bond strength appreciably weaker than the strength of the material of the liner 13. Such a construction would permit unfolding of the longitudinal fold 25 in a manner similar to that described above with the wider line of adhesive separating partially to increase the periphery of the liner in compensation for liner shrinkage.

From the foregoing, it will be seen that novel and advantageous provisions have been made for carrying out the desired end. However, attention is again directed to the fact that additional variations may be made in this invention without departing from the spirit and scope thereof as defined in the appended claims.

I claim:

1. A tubular member particularly adapted for being fabricated into a container which is capable of expanding under the influence of a packaged product comprising a tubular body, a longitudinal fold formed from the material of said body, said longitudinal fold being defined by first and second opposing generally parallel overlying freely unfoldable longitudinal portions movable relative to each other whereby internal pressure applied to a container fabricated from said tube causes unfolding of said overfolded portions from the generally parallel relationship toward a coplanar position to thus increase the body and prevent rupture thereof, and means for limiting the unfolding of said longitudinal fold and'preventing complete unfolding of said first and second overlying freely unfoldable longitudinal portions toward a coplanar relationship.

2. A tubular member particularly adapted for being fabricated into a container component which is capable of expanding under the influence of a packaged product comprising a tubular 'body, first means for providing a first increase in the volume of said body and second means for providing a second increase in the volume of said body only after said first means has provided said first volume increase whereby internal pressure applied to a container fabricated from said tube is precluded from rupturing said tube.

3. A tubular member particularly adapted for being fabricated into a container body which is capable of expanding under the influence of a packaged product comprising a tubular body, said tubular body having longitudinal seam means, said longitudinal seam means including first means for providing a first predetermined increase in the volume of said body and second means for providing a second predetermined increased in the volume of said body beyond said first increase only after said first increase in volume has occurred whereby internal pressure applied to a container fabricated from said tube is precluded from rupturing said tube.

4. The tubular member as defined in claim 3 where said first and second means additionally functions to prevent said seam means from rupturing under the influence of internal pressure.

5. An expandable joint construction comprising first and second lapped edge portions having respective first and second opposing surfaces and terminal edges, said second edge portion being joined at a juncture to an intergral overfolded portion thereof whereby said second and overfolded portions define a freely unfoldable fold, primary means joining said first and second edge portions between one of said edges and juncture, and secondary means also joining said first and second edge portions between one of said edges and said juncture.

6. A container comprising a body, said body being generally tubular in configuration and closed at one end portion thereof, said body being constructed from sheet material and having first and second lapped longitudinal edge portions, said first and second edge portions terminating in respective first and second edges, said second edge portion being joined at a juncture to an integral portion overfolded upon said second edge portion whereby said second and overfolded portions define a freely unfoldable longitudinal fold, and means both securing said first and second edge portions together and limiting the unfolding of said longitudinal fold to twice the distance between said means and said juncture whereby internal pressure applied to said container causes unfolding of said fold and thereby prevents the rupturing of the sheet material of said body.

7. A container comprising a body, said body being generally tubular in configuration and closed at one end portion thereof, said body being constructed from foldable material, a longitudinal fold formed from the material of said body, said longitudinal fold being defined by first, second and third opposing longitudinal portions of said body in generally parallel relationship in a first position but adapted for unfolding movement toward a generally coplanar relationship in a second position, said first and second portions being joined at a first juncture internally of said body and said second and third portions being joined at a second juncture externally of said body, one of said junctures being defined by adhesive means adhesively securing together terminal edges of at least two of said first, second and third opposing longitudinal portions, the distance between said junctures in the first position being generally one-half the distance between the junctures in the second position whereby unfolding of said longitudinal fold under the influence of a product in said body can take place.

8. A container comprising a body, said body being generally tubular in configuration and closed at one end portion thereof, said body being constructed of foldable material, a longitudinal fold formed from the material of said body, said longitudinal fold being defined by first, second and third opposing longitudinal portions of said body in generally parallel relationship in a first position but adapted for unfolding movement toward a generally coplanar relationship in a second position, said first and second portions being joined at a first juncture and said second and third portions being joined at a second juncture, said first juncture including first adhesive means adjacent edges of said first and second edge portions, second adhesive means between said second juncture and said first adhesive means, and the distance between said second adhesive means and said second juncture in the first position of said longitudinal fold being generally one-half the distance between said second juncture and the second adhesive means in the second position whereby unfolding of said longitudinal fold under the influence of a product in said body can take place.

9. A container comprising a body, said body being generally tubular in configuration and closed at one end portion thereof, said body being constructed of foldable material, a longitudinal fold formed from the material but adapted for unfolding movement toward a generally coplanar relationship in a second position, said first and second portions being joined at a first juncture and said second and third portions being joined at a second juncture, said first juncture including first adhesive means adjacent edges of said first and second edge portions, second adhesive means between'said second juncture and said first adhesive means, and the distance between said second adhesive means and said second juncture in the first position of said longitudinal fold being generally one-half the distance between said second juncture and the second adhesive means in the second position whereby unfolding of said longitudinal fold under the influence of a product in said body can take place, and the bond strength of said first adhesive means is weaker than the tear strength of said material.

10. A container comprising a body, said body being generally tubular in configuration and closed at one end portion thereof, said body being constructed of foldable material, a longitudinal fold formed from the material of said body, said longitudinal fold being defined by first, second and third opposing longitudinal portions of said body in generally parallel relationship in a first position but adapted for unfolding movement toward a generally coplanar relationship in a second position, said first and second portions being joined at a first juncture and said second and third portions being joined at a second juncture, said first juncture including a longitudinal line of adhesive between said first and second edge portions forming a longitudinal seam of said container, and the bond strength of said adhesive being appreciably weaker than the strength of said material whereby said adhesive partially separates after the longitudinal fold has fully unfolded to preclude rupture of the body material.

11. An expandable liner comprising a body formed of sheet material, said body including means whereby said body can expand under the influence of internal forces created by a product packaged in the body, said last mentioned means including a longitudinal fold formed by first, second and third opposing generally parallel overfolded freely unfoldable longitudinal portions movable relative to each other from a generally parallel relationship toward a coplanar relationship, said second and third portions being joined to each other by an integral longitudinal fold line, said first and second portions being joined to each other by adhesive means, and said adhesive means having a bond strength appreciably less than the strength of said sheet material whereby said liner can expand under the combined effects of the second and third portions freely unfolding under the pressure of a packaged product in said liner and at least a partial breakdown of the adhesive bond between the first and second portions without rupture of the liner material.

12. The expandable liner as defined in claim 11 wherein said first and second portions include free edges and additional adhesive means are provided between said free edges and said first mentioned adhesive means.

13. A container comprising at least an outer wrapper and an inner liner, said inner liner being capable of expanding under the influence of a packaged product and comprising a tubular body, first means for providing a first increase in the volume of said liner body, and second means for providing a second increase in the volume of said liner body only after said first means has provided said first volume increase where-by internal pressure applied to the liner by a product packaged therein is precluded from rupturing said liner, and one of said first and second means is not a folded portion of said inner liner.

14. A container comprising at least an outer wrapper and an inner liner, said inner liner being capable of expanding under the influence of a packaged product and including a tubular body, said tubular body including first and second lapped edge portions having respective first and second opposing surfaces, said first and second opposing surfaces including terminal edges, said second edge portion being joined at a juncture to an integral overfolded portion thereof whereby said second and overfolded portions define a freely unfoldable fold, and adhesive means securing said first and second lapped edge portions to one another.

References Cited by the Examiner UNITED STATES PATENTS JOSEPH R. LECLAIR, Primary Examiner.

DAVID M. BOCKENEK, Examiner. 

1. A TUBULAR MEMBER PARTICULARLY ADAPTED FOR BEING FABRICATED INTO A CONTAINER WHICH IS CAPABLE OF EXPANDING UNDER THE INFLUENCE OF A PACKAGED PRODUCT COMPRISING A TUBULAR BODY, A LONGITUDINAL FOLD FORMED FROM THE MATERIAL OF SAID BODY, SAID LONGITUDINAL FOLD BEING DEFINED BY FIRST AND SECOND OPPOSING GENERALLY PARALLEL OVERLYING FREELY UNFOLDABLE LONGITUDINAL PORTIONS MOVABLE RELATIVE TO EACH OTHER WHEREBY INTERNAL PRESSURE APPLIED TO A CONTAINER FABRICATED FROM SAID TUBE CAUSES UNFOLDING OF SAID OVERFOLDED PORTIONS FROM THE GENERALLY PARALLEL RELATIONSHIP TOWARD A COPLANAR POSITION TO THUS INCREASE THE BODY AND PREVENT RUPTURE THEREOF, AND MEANS FOR LIMITING THE UNFOLDING OF SAID LONGITUDINAL FOLD AND PREVENTING COMPLETE UNFOLDING OF SAID FIRST AND SECOND OVERLYING FREELY UNFOLDABLE LONGITUDINAL PORTIONS TOWARD A COPLANAR RELATIONSHIP. 